1. Field of the Invention
This invention relates in general to hydromechanical automatic reversing devices and has specific reference to an improved device of this type intended more particularly for an easy adaptation thereof to linear hydraulic rams, jacks or like actuators and cylinders, and for controlling a continuous reciprocating motion of the piston of the device while permitting the adjustment thereof at both ends of its stroke, this apparatus combining an outstanding efficiency with a high degree of precision and fidelity of the reversing positions, a quick reversing of the direction of motion and very high rates of operation.
2. Description of the Prior Art
Among hitherto known devices of this character, designed for reversing the direction of movement of the movable member of hydraulic cylinders, rams, jacks and the like, the following may be cited:
(a) hydrochemical systems or purely mechanical mmeans, such as lugs or cams, fixed to the cylinder or to the mechanical device to be driven, which are adapted, at the end of the stroke, to release a mechanism, as a rule spring means, capable of moving the spool of the distributor valve of the cylinder, and thus reversing the piston movement. However, these known systems are objectionable, notably on account of their lack of precision in the cylinder reversing positions, of the relatively long time required for reversing the piston movement, the limited frequency of the reciprocating movements, and a generally fragile, therefore scarcely reliable construction; PA1 (b) hydromechanical devices fixed to the jack and adapted, at the end of the piston stroke, to release a hydraulic monitoring valve controlling the reversing of the main distribution valve of the ram. These devices are objectionable, notably on account of the following drawbacks: lack of precision in the ram reversing positions, relatively long time required for achieving the reversing, limited frequency of the reciprocating movements, and rather complicated and therefore expensive construction; PA1 (c) electromechanical or electrical devices such as switches, proximity detectors, photo-electric cells, etc., actuated at the end of the ram piston stroke, for controlling through an electric switchboard the reversing of a distributor solenoid-valve. This system is characterized by the same inconveniences as those described in paragraph (b) hereinabove; PA1 (d) reversing devices based on the use of special rams actuated by servovalves or servo-controlled rams. In both cases, the hydraulic system and the arm are associated with an electrical control system. These known devices are objectionable mainly for the following reasons: complicated and therefore costly arrangement, difficult and expensive exploitation, due to the specific requirements of the relatively sophisticated apparatus implemented.